Cooling device and construction machine or working machine equipped with the same

Abstract

A cooling device includes: a cooling fan; a shroud provided at an outer circumferential side of the cooling fan; an inner circumferential wall provided on the shroud and adjacent to the outer circumference of the cooling fan so as to surround the cooling fan; an outer circumferential wall provided to surround the inner circumferential wall. An air-flow-direction downstream side end of the outer circumferential wall is positioned at a further downstream position in an air flow direction than an air-flow-direction downstream side end of the inner circumferential wall. The cooling fan is rotatable within a space provided on a radially inner side of the inner circumferential wall. The air-flow-direction downstream side end of the outer circumferential wall is provided at a further upstream position in the air flow direction than an air-flow-direction downstream side end of the cooling fan.

The invention claimed is:  
     
       1. A cooling device, comprising:
 a cooling fan; 
 a shroud provided at an outer circumferential side of the cooling fan; 
 an inner circumferential wall provided on the shroud and spaced apart from an outer circumference of the cooling fan in a radial direction of the cooling fan by a predetermined distance to surround the cooling fan, the inner circumferential wall being outside of and facing the cooling fan in the radial direction of the cooling fan; and 
 an outer circumferential wall provided to surround the inner circumferential wall, the outer circumferential wall being outside of and facing the inner circumferential wall in the radial direction of the cooling fan, an air-flow-direction downstream side end of the outer circumferential wall being positioned downstream, in an air flow direction, of an air-flow-direction downstream side end of the inner circumferential wall, at least a portion of the outer circumferential wall including a cylindrical surface, 
 wherein the cooling fan is rotatable in a space on a radially inner side of the inner circumferential wall, 
 wherein an air-flow-direction upstream side end of the cooling fan is positioned upstream, in the air flow direction, of an air-flow-direction upstream side end of the inner circumferential wall and an air-flow-direction upstream side end of the outer circumferential wall, 
 wherein the air-flow-direction downstream side end of the outer circumferential wall is positioned upstream, in the air flow direction, of an air-flow-direction downstream side end of an outer circumferential edge of the cooling fan, and 
 wherein an exterior covering ratio is in a range of 55 to 95%, the exterior covering ratio being a ratio of (i) an air-flow-direction length of a portion of the cooling fan covered by the shroud and the outer circumferential wall to (ii) a maximum air-flow direction length of the cooling fan in the air flow direction of the cooling fan. 
 
     
     
       2. The cooling device according to  claim 1 , wherein at least one of the inner circumferential wall and the outer circumferential wall is a ring that is consecutively provided around a rotation shaft of the cooling fan. 
     
     
       3. The cooling device according to  claim 1 , wherein the exterior covering ratio is in a range of 70 to 95%. 
     
     
       4. The cooling device according to  claim 3 , wherein the exterior covering ratio is in a range of 70 to 80%. 
     
     
       5. The cooling device according to  claim 1 , wherein an interior covering ratio is in a range of 45 to 85%, the interior covering ratio being a ratio of (i) an air-flow-direction length of a portion of the cooling fan covered by the shroud and the inner circumferential wall to (ii) the maximum air-flow-direction length of the cooling fan in the air flow direction of the cooling fan. 
     
     
       6. The cooling device according to  claim 1 , wherein at least one of the inner circumferential wall and the outer circumferential wall is integrated with the shroud. 
     
     
       7. The cooling device according to  claim 1 , wherein at least one of the inner circumferential wall and the outer circumferential wall is formed by a member different from the shroud. 
     
     
       8. The cooling device according to  claim 7 , further comprising:
 an annular base connecting the inner circumferential wall to the outer circumferential wall. 
 
     
     
       9. The cooling device according to  claim 1 , wherein at least one of the inner circumferential wall and the outer circumferential wall includes a cylindrical portion extending in parallel to the air flow direction. 
     
     
       10. The cooling device according to  claim 1 , wherein at least one of the inner circumferential wall and the outer circumferential wall includes a diameter-expanded portion of which an inner diameter increases toward downstream in the air flow direction. 
     
     
       11. A construction machine or a work machine, comprising the cooling device according to  claim 1 . 
     
     
       12. The cooling device according to  claim 1 , wherein the cylindrical surface is radially spaced apart from the cooling fan and curved to correspond to the radial curvature of the outer circumferential edge of the cooling fan. 
     
     
       13. The cooling device according to  claim 1 , wherein at least a portion of the cylindrical surface tracks the radial curvature of the outer circumferential edge of the cooling fan. 
     
     
       14. The cooling device according to  claim 13 , wherein the entire cylindrical surface tracks the radial curvature of the outer circumferential edge of the cooling fan. 
     
     
       15. The cooling device according to  claim 1 , wherein the inner circumferential wall and the outer circumferential wall define an annular space therebetween that surrounds the cooling fan. 
     
     
       16. The cooling device according to  claim 1 , wherein the cylindrical surface of the outer circumferential wall surrounds an entire circumference of the inner circumferential wall. 
     
     
       17. The cooling device according to  claim 1 , wherein each of the inner circumferential wall and the outer circumferential wall is a ring that is consecutively provided around a rotation shaft of the cooling fan.